The invention is in the field of carbon baking; more particularly, the invention relates to a container means in which carbon products are placed during baking.
Carbon products, such as electrodes, are made from particulate carbon mixed with a suitable binder, such as tar or pitch. The mixture is molded or formed to a desired form and baked in a furnace until the volatile matter and liquid tar are driven off and the carbon product has achieved a desired density and conductivity. When heated, during the baking, the carbon products have a tendency to soften and to deform.
To overcome the problems of deformation of the carbon products and handling the liquid tar, particularly in production of carbon electrodes, suitable containers, such as sagger cans, have been used. These sagger cans are solid metal containers shaped similarly to the electrode. When the carbon product is formed at lower temperatures, it retains its shape. It is centered in the metal can in which it will be baked. The space between the inside of the can and the outside of the electrode is filled with a mixture of coal, coke and sand particles. This process is somewhat laborous as the gap between the carbon product and the solid metal can must be manually filled. The use of coal, coke and sand particles creates atmospheric dust resulting in particulate pollution problems. The metal can is made out of a solid carbon steel or alloy steel plate. The loaded sagger can is placed in the furnace where it is raised from room temperature to approximately 1600.degree. F. at a rate varying from 1.degree. F. to 10.degree. F. per hour. The sagger can supports the packed electrode so that it will not deform. Volatiles in vapor form pass through the coal, coke and sand particles to the top of the can where they leave the can and enter the furnace atmosphere. Solid carbon residue of the liquid tar released remains in the can within the mixture of coal, coke and sand particles.
The packing mixture of coal, coke and sand particles has poor heat transfer properties and the path through which the volatiles have to travel to leave the can is limited to the open top.
In U.S. Pat. No. 1,440,724, An Electrode for Electric Furnaces and Process for Manufacturing the Same by C. W. Soderberg, electrodes are manufactured by tapping or pressing a suitable electrode mass into a metallic mantle. The mantle in the preferred form serves not only as a conductor and as a protection for the electrode mass but also as a mechanical means of retaining and supporting the same. The electrodes are baked in the same furnace as they are being used. The mantle is built up of sections suitably fastened together. It is made with internally extending ribs which are provided with projections. These ribs and projections afford means of distributing current in the carbonaceous material and act as a mechanical support, therefore, to prevent slipping of the carbonaceous material in the mantle. The mantle is further preferably perforated so that gas produced by the baking may escape without deforming the mantle.
The Soderberg patent describes a special case for an electrically baked electrode. The electrode is continually formed in the furnace and is baked in part by the heat from the melting metal in the furnace and from the electric current through the mantle. There is no provision made for liquid tars released during the baking of the electrode. The electrode is consumed within the same furnace where it is being formed. Additionally, there is no provision or need for removal of the electrode from the mantle for use elsewhere.
In a carbon baking furnace, provision must be made for liquid tars released during baking and there must be the ability to remove the electrodes from the container means in which they are baked. It is desirable to bake the carbon products as efficiently as possible.